1. Field
Embodiments of the invention relate to blowoff valves for releasing excess air pressure. More specifically, embodiments of the invention relate to a multi-chamber blowoff valve configured to be used with a supercharger in a vehicle.
2. Related Art
Superchargers, turbochargers, and the like provide additional air to internal combustion engines. The additional air increases the power and work performed by the internal combustion engine by increasing the amount of fuel that can be burned at a given time. In essence, the supercharger acts as an air compressor to force air into the engine. Often, the air will travel from an outlet of the supercharger to an engine-air interface (typically a throttle) for the engine via a tubing, a piping, a direct connection, or the like.
When the internal combustion engine is spinning rapidly, the supercharger in turn also spins rapidly. This mutual relationship is beneficial because the supercharger is feeding the additional air needed for additional increases in speed and power. However, sudden decreases in speed and power (such as by the driver removing their foot from the accelerator, thus closing the throttle) can be problematic to superchargers of the prior art. Because there is a slight delay in compression of air by the supercharger following a reduction in speed and power, there is often an excessive abundance of air in a duct system of the vehicle when the throttle of the engine is closed.
This abundance of air in the duct system can be problematic for a few reasons. First, the excessive air pressure can cause damage to engine components such as the throttle. Second, the excessive air pressure can cause the air to travel back to the supercharger and damage supercharger components.
Typically, the air pressure in the duct is at a higher pressure than the air in the engine manifold. This can be caused by various restrictions from the air outlet to the engine manifold such as an intercooler, throttle blade, tubing bends and length, etc. If the blowoff valve's ability to contain the air pressure in the ducting is overcome, the valve can be forced open and air will be released from the ducting and not into the engine, reducing power output. Air pressure and vacuum forces acting inside the chamber are what actuates the valve. To keep the blowoff valve shut when duct pressures are higher than manifold pressures, the area of the piston within the blowoff valve must be larger than the sealing surface of the duct, therefore compensating for the greater pressure in the ducting.
Often, the available space within an engine compartment is limited. Therefore, providing a blowoff valve with a minimal volume and cross-sectional area is advantageous to be able to add to existing vehicles. Also, a smaller valve will weigh less, which is desirable in racing applications. Further, larger superchargers require a larger blowoff valve to handle increased airflow and increased pressure differentials created by the increased airflow.